Actuator and locking means therefor



L A M E D O B Q R ACTUATOR AND LOCKING MEANS THEREFOR 2 Sheets-Sheet 1 v Filed Aug. 51, 1954 INVENTORS Ray C. Bodem BY James W Light Their Affarney Nov. E957 R. c. BODEM ETAL 29811319951 ACTUATOR AND LOCKING MEANS THEREFOR Filed Aug. 51, 1954 2 Sheets-Sheet 2 INVENTORS Fl 4 Roy 0. Bade/n y James W Light M War/n The/r Aflorney ACTUATOR AND LOCKiNG MEANS THEREFUR Roy C. Bodenn, Dayton, and James W. Light, Greenville,

Ohio, assignors to Gcnerai Motors Corporation, Detroit, Mich, a corporation of Delaware Application August 31, 1954, Serial No. 453,369

11 Claims. (Cl. 121-4fl) This invention pertains to self-locking actuators, and particularly to an improved actuator assembly of this type.

Heretofore, actuators of the type including a cylinder having disposed therein a reciprocable piston capable of fluid pressure actuation in both directions, have embodied various types of locking means which operate to prevent relative movement between the piston and cylinder when the actuator is inactive. For example, a friction type brake is disclosed in copending application Serial No. 394,660, new Patent #2,774,336, filed November 27, 1953, in the name of Howard M. Geyer; a toothed type brake is disclosed in the Geyer Patent No. 2,643,642; and a roller type brake is disclosed in copending application Serial No. 296,607, filed July 1, 1952, in the name of Howard M. Geyer, now Patent No. 2,705,939. All of the aforementioned locking actuators include a screw shaft operatively connected to the piston so as to rotate upon piston reciprocation, the locking means being operatively associated with the screw shaft. This invention obviates the necessity of a screw shaft, and, hence, greatly simplifies the actuator assembly without etfecting its operation and advantageous features. Accordingly, among my objects are the provision of locking means for a fluid pressure operated actuator; the further provi-' sion of locking means which are automatically released upon the application of fluid pressure to the cylinder; and the still further provision of actuator locking means which are automatically operable to restrain piston movement upon the interruption of fluid pressure application to the cylinder due to the load to which the actuator is subjected.

The aforementioned and other objects are accomplished in the present invention by the provision of a roller lock including a stationary locking bar and a plurality of locking rollers. Specifically, the actuator comprises a cylinder having disposed therein a reciprocable piston assembly capable of fluid pressure actuation in both directions. The piston assembly includes a diametrically slotted skirt, or annular sleeve portion which slidably supports a piston head capable of movement relative thereto. Thus, it may be said that the annular sleeve, or skirt, which is integral with a piston rod, has a lost motion connection with the piston head. The piston head is connected to four spaced, transversely extending lock release pins which are disposed adjacent the ends and on opposite sides of a pair of locking rollers. The axis of the locking rollers are disposed in a plane located substantially at right angles to the pins. The locking rollers engage a centrally disposed, stationary locking bar, and are operatively associated with a pair of cam members disposed on opposite sides of the locking bar and operatively connected with the piston assembly so as to be movable therewith.

When the actuator is inactive, and, hence, fluid under pressure is not being applied to the cylinder, the load to which the actuator piston rod is subjected will cause the locking rollers to be wedged between the locking bar and the cam member, thereby restraining movement of the piston assembly. During locking movement of the piston rod, the piston head, which frictionally and sealingly engages the cylinder, will remain stationary, by reason of the lost motion connection between the piston head and the rod assembly. Thus, when the actuator is inactive, the actuator will be locked by the load imposed upon the actuator rod. As stated hereinbefore, the piston head is adapted for reciprocable movement relative to the rod assembly, which relative movement is limited by an annular shoulder on the rod and an end plate spaced therefrom. Moreover, as only the piston head assembly frictionally and sealingly engages the cylinder walls, upon the interruption of fluid pressure application to the cylinder, the load imposed upon the piston rod will effect movement of the piston rod relative to the piston head.

The locking means are automatically released upon the application of fluid pressure to the cylinder in the following manner. if pressure fluid is applied to the cylinder in assisting relation to the load, the piston head assembly will move relative to the piston rod assembly, thereby moving the locking rollers out of wedging relation with the cams and locking bar. Thereafter, the head assembly and the rod assembly will move in unison. However, if pressure fluid is applied to the cylinder in opposition to the applied actuator load, relative movement between the piston head assembly and the rod assembly will occur when the applied unit area pressure exceeds the applied load unit area pressure. Thus, the rod assembly will 'be moved relative to the head assembly, thereby moving the locking cams out of wedging relation with the locking rollers so as to release the locking means. Thus, the locking means of the instant actuator may be called load sensitive.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a view, partly in section and partly in elevation, of an actuator constructed according to this invention.

Fig. 2 is a fragmentary view, partly in section and partly in elevation, illustrating the locking means in the locked condition.

Fig. 3 is a view similar to Fig. 2 with the locking means in the released position.

Fig. 4 is a fragmentary sectional view taken generally in the direction of arrow 4 in Fig. 1 with the locking means in the locked condition.

With particular reference to Fig. l of the drawings, the actuator includes a cylinder 10 having externally threaded portions 11 and 12 adjacent opposite ends thereof. The threaded portion 11 receives a head cap assembly 13 which is formed with an extend port 15 and an integral fixture portion 17 by which means the actuator cylinder may be attached to a fixed support, not shown. The threaded portion 12 of the cylinder receives a tail cap assembly 14 having a retract port 16 and a centrally disposed opening 13. The cylinder has disposed therein a piston assembly, generally designated by the numeral 20, capable of fluid pressure actuation in both directions relative to the cylinder. The piston assembly includes a recessed piston rod 21, which projects through the opening 18 in the head cap assembly 14, the rod 21 having an integral fixture portion 22 which is arranged for connection to a relatively movable load, not shown.

The piston rod 21 is formed with an annular shoulder 23 intermediate its ends, the diameter of the annuiar shoulder being less than the bore of the cylinder 10, as depicted in Figs. 2 through 4. The piston rod 21 is also formed with an annular skirt, or sleeve portion, 24 having diametrically aligned openings 25 and 26. The end of the sleeve portion 25 has attached thereto by means of circumferentially spaced bolts 27, an end plate 28. The piston assembly 20 also includes a reciprocable head assembly 29, which is slidably supported on the sleeve portion 24 between the shoulder 23 and the end plate 28.

The piston head 29 sealingly engages the sleeve portion 24 and the internal periphery of the cylinder 10. In addition, the piston head 29 frictionally engages the bore of the cylinder 10, so that the rod assembly 21 is capable of movement relative thereto. To facilitate relative movement between the piston rod assembly 21 and the piston head 29, a lost motion connection is provided between the rod assembly 21 and the piston head. This lost motion connection results from the fact that the distance between the shoulder 23 and the plate 28 is greater than the longitudinal extent of the piston head 29.

The actuator assembly also includes a locking bar 40 which is attached to the head cap assembly 13 by means of bolts 41. The locking bar 40 is coaxially disposed within the cylinder and includes a portion having spaced parallel flat surfaces 42 and 43. Inasmuch as the locking bar is attached to the head cap assembly 13, which is, in turn, rigidly connected with the cylinder 10, it will be appreciated that the locking bar 40 is restrained against movement relative to the cylinder 10.

The piston assembly also includes releasable locking means for preventing relative movement between the piston rod 21 and the cylinder 10 when the actuator is inactive. The locking means includes a pair of U-shaped cam members and 31 disposed on opposite sides of the locking bar 40, the leg portions of the U-shaped members 30 and 31 engaging the flat surfaces 42 and 43 of the locking bar. The interior surface of the base of each U-shaped member 32 and 33, respectively, is substantially V-shaped. Thus, the portions of the inner surface of the base of each U-shaped member adjacent the legs is spaced a lesser distance from the locking bar than the medial portion thereof.

The piston head assembly 29 carries two pairs of spaced, transversely extending lock release pins 34 and which extend transversely within the cylinder 10. The pins 34 project through the diametrically aligned openings 25 and 26 in the sleeve portion 24. The locking means also include a pair of locking rollers 36 and 37 disposed on opposite sides of the locking bar and confined within the U-shaped cam members 30 and 31, respectively. Each end of the locking rollers 36 includes a reduced diameter portion 38, while each end of the rollers 37 includes a reduced diameter portion 39. The reduced diameter portions of the rollers 36 and 37 are disposed between the pair of lock release pins 34 on one side and between the pair of lock release pins 35 on the other side.

The locking means operate in the following manner. When the rollers 36 and 37 are wedged between the inclined bottom surfaces of the U-shaped members 30 and 31, respectively, and the flats 42 and 43, respectively, of the locking bar 40, movement of the piston assembly 20 relative to the cylinder 10 is precluded. This phenomenon is depicted in Fig. 2. However, as shown in Fig. 3, when the locking rollers 37 and 38 are maintained in the medial portion of the cam members 30 and 31, respectively, the piston assembly 20 can be moved relative to the cylinder 10 in either direction by the application of fluid under pressure.

Operation Operation of the self-locking actuator is as follows. Assuming that the fixture 17 is connected to a fixed support, while the fixture 22 is connected to a load, which load is acting in a direction tending to effect movement of the rod assembly 21 to the left, as viewed in the draw-v ings, in the absence of fluid pressure application to the cylinder, the applied load will lock the actuator, as depicted in Fig. 2. Thus, by reason of the head assembly 29 frictionally engaging the cylinder 10, and by reason of the lost motion connection between the head assembly 29 and the rod assembly 21, the rod 21 will move to the left under the applied load relative to the head assembly 29. Inasmuch as the cams 30 and 31 are constrained for movement with the rod assembly 21 by reason of their confinement between the shoulder 23 and the end plate 27, the cams 30 and 31 will move into wedging engagement with the rollers 36 and 37, which are then stationary. In other words, the rollers 36 and 37 will become wedged between the surfaces 32 and 33 of the U- shaped cams 30 and 31 and the flats 42 and 43 of the locking bar during relative movement between the rod assembly 21 and the head assembly 29 due to the applied actuator load depicted by the arrow 50 in Fig. 1. In order to release the locking means so as to permit adjustment in the position of the load device, fluid under pressure must be applied to the actuator cylinder. If pressure fluid is applied to the retract chamber through the retract port 16 while the extend chamber 46 is connected to drain through the extend port 15, it is apparent that the fluid under pressure is being applied to the actuator in a direction assisting the applied load. By reason of the fact that the head assembly 29 is capable of movement relative to the rod assembly 21, the fluid pressure acting upon the head assembly 29 will move the head assembly to the left, as viewed in Fig. 2, relative to the rod assembly 21. Accordingly, the two pairs of lock release pins 34 and 35 will move to the left with the head assembly 29 and move the locking rollers 36 and 37 out of wedging relation with the earns 30 and 31 and surfaces 42 and 43, respectively, of the locking bar 40. When the locking rollers 36 and 37 have been moved to the full line position shown in Fig. 3, the entire piston assembly 20, including the head 29 and the rod 21, will move to the left relative to the cylinder 10 under the urge of fluid under pressure in the retract chamber 45.

However, if pressure fluid is applied to the extend chamber 46 while the retract chamber 45 is connected to drain, with the applied load acting in the direction of arrow 50, the following sequence of events will transpire. When the unit area pressure acting on the end plate 28, which results from the application of fluid pressure to the extend chamber 46, exceeds the unit area pressure acting on the rod assembly 21 due to the applied load in the direction of arrow 50, the rod assembly 21 will move relative to the then stationary head assembly 29. Thus, the cams 30 and 31 will move to the right, as viewed in Fig. 2, while the head assembly 29 remains stationary. When the rod assembly 21 has moved from the position of Fig. 2 to the position of Fig. 3, the locking means will be released, thereby permitting movement of the entire piston assembly 20 to the right relative to the cylinder 10.

From the foregoing, it is manifest that the present invention results in a self-locking actuator which is structurally more simple than actuators heretofore designed. Furthermore, the instant actuator does not require an independent lock release piston and cylinder combination for releasing the locking means concurrently upon the application of fluid pressure to the cylinder, which arrangement was necessary in the actuators constructed according to the hereinbefore mentioned patents.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An actuator including in combination, a cylinder, a reciprocable piston assembly disposed in said cylinder capable of fluid pressure actuation in both directions, a stationary locking bar disposed in said cylinder, and twoway locking means carried by said piston assembly and cooperable with said locking bar for preventing reciprocatlon of said piston assembly in the absence of fluid pressure application to said cylinder under the action of the load applied to said piston assembly, said locking means comprising cam means and roller means adapted to be wedged between said cam means and said. locking bar.

2. An actuator including in combination, a cylinder, a reciprocable piston assembly disposed in said cylinder capable of fluid pressure actuation in both directions, a stationary member disposed in said cylinder, and load applied, fluid pressure releasable, two-way locking means carried by said piston assembly and cooperable with said stationary member for preventing movement of said piston assembly in the absence of fluid pressure application to said cylinder, said locking means comprising cam means and roller means adapted to be wedged between said cam means and said stationary member.

3. An actuator including in combination, a cylinder, a reciprocable piston assembly disposed in said cylinder capable of fluid pressure actuation in both directions, a stationary member disposed within said cylinder, and load applied, fluid pressure releasable locking means carried by said piston assembly and cooperable with said stationary member for preventing piston movement in the absence of fluid pressure application to said cylinder, said locking means including a pair of cams disposed on opposite sides of said stationary member and a pair of rollers adapted to be wedged between said cams and said stationary member.

4. An actuator including in combination, a cylinder, a reciprocable piston assembly disposed in said cylinder capable of fluid pressure actuation in both directions, a stationary member disposed within said cylinder, and load applied, fluid pressure releasable locking means carried by said piston assembly and cooperable with said stationary member for preventing piston movement in the absence of fluid pressure application to said cylinder, said locking means comprising a pair of U-shaped cam members disposed on opposite sides of said stationary member and having V-shaped internal surfaces, a pair of rollers capable of wedging relation between said cam members and said stationary member, and means for effecting relative movement between said rollers and said earn members so as to move said rollers into and out of wedging relation with said cam members and stationary member.

5. The combination set forth in claim 4 wherein said last recited means comprises a plurality of pins, the axes of which are disposed at right angles to the axes of said rollers, and wherein said piston assembly includes a rod portion and a head portion capable of relative movement, said pins being attached to and movable with said head portion.

6. The combination set forth in claim 5 wherein said rod portion includes an annular skirt upon which said head portion is slidably supported, and means limiting relative movement between said head portion and said rod portion.

7. An actuator assembly including in combination, a cylinder, a reciprocable piston assembly disposed in said cylinder, said piston assembly comprising a rod having an annular sleeve portion and a head assembly slidably mounted on said sleeve portion for movement relative thereto, a stationary member disposed within said cylinder and extending through said piston assembly, a pair of U-shaped cams disposed on opposite sides of said stationary member and constrained for movement with said rod, and means carried by said head capable of wedging relation between said cams and said stationary member for preventing movement of said piston assembly when the actuator is inactive.

8. The combination set forth in claim 7 wherein said piston assembly includes means for limiting relative movement between said head assembly and said rod.

9. The combination set forth in claim 7 wherein the means carried by said head assembly comprise a plurality of pins and a pair of locking rollers disposed on opposite sides of said stationary member, the ends of said locking rollers being confined between the ends of pairs of said pins and the axes of said rollers being disposed in a plane 90 to the plane of the axes of said pins.

10. The combination set forth in claim 9 wherein said stationary member is formed with spaced parallel flat surfaces, and wherein said cam members are formed with V-shaped internal surfaces, said locking rollers being capable of wedging relation therebetween.

11. The combination set forth in claim 7 wherein said head assembly frictionally and sealingly engages said cylinder, wherein said rod includes an annular shoulder limiting relative movement betweensaid head and rod in one direction, and an annular plate for limiting relative movement between the head and rod in the other direction.

References Cited in the file of this patent UNITED STATES PATENTS 

